The invention relates to the field of underwater optical fiber connectors, and more particularly to underwater-mateable, optical fiber connectors permitting cyclable, direct, fiber-to-fiber butt connection in a high-pressure, hostile undersea environment.
The increased use of fiber-optic systems in the undersea environment has created a need for underwater fiber-optic cable and connector systems. Connectors for optical fibers which can be operated underwater have been developed. Examples of such connectors are found in my U.S. patent application Ser. No. 623,037, now abandoned, and my U.S. patent application Ser. No. 623,038, both assigned to the assignee of this patent application.
While the underwater connectors exemplified by these patent applications do provide a fiber optic channel interconnection which is cyclable underwater, both employ lensing arrangements to transmit light energy between the optical fibers that are being connected. The advantages of these connectors are that they are rugged and protect the optical fibers themselves from exposure to the seawater environment where they could suffer mechanical or corrosive damage. The disadvantage of these lens-type connectors is that, by using lenses, the inherent loss of light energy through the connector is increased. In lensed connectors, energy is lost at the junctions between the lens and fiber, by imperfections in the lenses themselves, by reflections at fiber and lens interfaces, and due to mechanical misalignments.
As is known, very low loss optical junctions are achievable in the laboratory by butting the terminal ends of two fibers directly together within a precision alignment device such as a capillary tube. Advances in connector technology for glass lightguides have provided practical solutions to the problem of butt-joining two optical fibers in a benign, dry environment. However, fiber-to-fiber splicing in an undersea environment presents problems of considerably more difficulty than those encountered in the laboratory. In the undersea environment, when connecting optical fibers, the fibers must be kept from exposure to seawater in order to reduce the possibility of corrosion of the fibers, which would result in increased connection losses. Further, optical fibers are small and very fragile and an underwater connector must provide for handling them with great care yet with great precision. Finally, an undersea fiber-to-fiber connector must be able to carry the fibers to connecting registration many times with predictably repeatable results.
The meritorious effect of the connector of the invention lies in the provision of a controlled, prophylactic environment for optical fibers which can be taken to any ocean depth and within which a low-loss, fiber-to-fiber connection can be made repeatably without exposing the mated fibers to the hostile seawater environment.
It is therefore a primary object of the present invention to provide a connector making a cyclable, low-loss fiber optic junction that is usable underwater.
Another object is to provide such a connector that can withstand the threats of a seawater environment.
Still another object of this invention is to provide a low-loss, fiber-to-fiber connector that can be mated and demated repeatedly in a high ambient pressure without damage to the optical fibers.